LaMotte COD Plus Colorimeter 1922-EX2 - Manual (Page 104)

PHOSPHATE - LOW RANGE
ASCORBIC ACID REDUCTION METHOD • CODE 3653-SC
QUANTITY CONTENTS CODE
60 mL *Phosphate Acid Reagent
*V-6282-H
5 g *Phosphate Reducing Reagent
*V-6283-C
1 Pipet, 1 mL, plastic
0354
1 Spoon, 0.1 g, plastic
0699
*WARNING: Reagents marked with a * are considered hazardous substances. Material
Safety Data Sheets (MSDS) are supplied for these reagents. For your safety read label
and accompanying MSDS before using.
Phosphorus is an important nutrient for aquatic plants. The amount found in
water is generally not more than 0.1 ppm unless the water has become polluted
from waste water sources or excessive drainage from agricultural areas. When
phosphorus is present in excess of the concentrations required for normal
aquatic plant growth, a process called eutrophication takes place. This creates a
favorable environment for the increase in algae and weeds. When algae cells
die, oxygen is used in the decomposition and fish kills often result. Rapid
decomposition of dense algae scums with associated organisms give rise to foul
odors and hydrogen sulfide gas.
APPLICATION:
Drinking, surface and saline waters; domestic and industrial
wastes (Method based on reactions that are specific for
orthophosphate).
RANGE: 0.00 – 3.00 ppm Orthophosphate
METHOD: Ammonium molybdate and antimony potassium tartrate
react in a filtered acid medium with dilute solution of PO
4
–3
to form an antimony-phosphomolybdate complex. This
complex is reduced to an intense blue colored complex by
ascorbic acid. The color is proportional to the amount of
phosphate present. (Only orthophosphate forms a blue color
in this test.) Polyphosphates (and some organic phosphorus
compounds) may be converted to the orthophosphate form
by sulfuric acid digestion. Organic phosphorus compounds
may be converted to the orthophosphate form by persulfate
digestion.
SAMPLE
HANDLING &
PRESERVATION: If benthic deposits are present in the area being sampled,
great care should be taken not to include these deposits. If
the analysis cannot be performed the same day of collection,
the sample should be preserved by the addition of 2 mL of
concentrated sulfuric acid or 40 mg mercuric chloride per
liter and refrigerated at 4°C.
COD PLUS TEST PROCEDURES 6/02 PHOSPHATE - LOW RANGE 1/3